Process for the resolution of gas mixtures



May 28, 1935.

M FRNKL PROCESS FOR THE RESOLUTION OF GAS MIXTURES F'led'OCt. 14, 1951 2 Sheets-Sheet ll IV.. m.

Mtv.

'WU IWI' MII May 28, 1935.4 M. FRNKL 2,002,940

PROCESS FOR THE RESOLUTION OF GAS MIXTURES Filed Oct. 14, 1931 2 Sheeis-Sheet 2 KKL @SQ YR; WS@

gerentes May 2s, ross UNITED STATES` man PATENT GFFICE IRCESS FOR THE RESOLUT-ON F GS MXTURES Application (lictober 14, 1931, Serial No. 568,714 In Germany May 20, 1931 -14 Claims.

The invention relates to a process and an apparatus for the resolution of gas mixtures into component parts. It more particularly relates to a process for the separation of air into oxygen and nitrogen and includes correlated improvements and discoveries whereby the separation of oxygen and nitrogen is enhanced.

The invention is in certain of its characteristics similar to that described in my co-pending application, Serial No. 437,204, filed March 19, 1930 and which issued as Patent No. 1,970,299, August 14, 1934. In this application there is described a process wherein the loss of compression energy which is-entailed in the total compression of the gas mixture necessary for carrying out an emcient sublimation eiect of deposited H2O and CO2 is reduced by not liquefying a certain portion of the'compressed gas mixture, but detensioning it in an expansion engine to atmospheric pressure, while performing work and yielding cold, and preferably after previous preliminary resolution of the gas mixture in a rectier operated at the condensation pressure. It may also be eifected with a subsequent resolution of the exhaust of an expansion engine in a rectier which operates at atmospheric pressure. In both cases therefore, the total air to be resolved is compressed to the condensation pressure, i. e. 3 lto 5` atmospheres absolute, and about one-half to three-quarters 30 thereof is liquefied in order to obtain the necessary washing liquid, while the other portion is detensioned in an expansion engine in order to produce the additional cold required Vfor covering the cold losses. It is an'object of the invention to provide a process in which the loss of compressionenergy normally Voccurring during the resolution of a ligas mixture with total compression is reduced.

i Itis a further object of the invention to pro- 40 vide a process for the separation of oxygen and nitrogen from air in which only a part of the air is compressed to condenser pressure, the other portion being simply blown in.

Another object of the invention is to provide a process with reduced compression losses and which is applicable for the production of oxygen of various degrees of purity, as for example a 42 per cent or a 47 per cent oxygen containing mixture.

50 A further object of the invention is to provide a process in which an exchange of cold is effected between the ingoing air and the outgoing separated components by means of regenerators with alternate periodical reversal.

It is also an object of the invention to provide an apparatus suitable for; effecting separation of gas mixtures into component parts and comprising means for eecting a reduction in compression and cold losses.

Other objects of the invention will in part 5 be obvious and will in part appear hereinafter.

The invention accordingly comprises the several steps and the relation of one or more of such steps with respect to each of the others, and the apparatus embodying features of construction, l0 combinations of elements and arrangement of parts which are adapted to effect such steps, all as exemplified in the following detailed disclosure, and the scope of the invention will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention reference should be had to the following detailed description taken in connection With the accompanying drawings, in which:

Fig. 1 illustrates diagrammatically an arrangement of apparatus in which the process 'may be practiced with withdrawal of a portion of the compressed air prior to liquefaction, and

Fig. 2 shows diagrammatically an apparatus in 25 which the process may be practiced utilizing a portion of the compressed air after resolution for further cooling and expansion to compensate for compression loss.

In'the practice of the invention a reduction 30 in the loss due to compressing the entire gas mixture to condenser pressure i. e., the pressure at which liqueed gas is produced under prevail- Aing conditions of cold, such as normally occurs during the resolution of air, is effected by compressing only one-half of the air to be resolved to the condensation pressure, this pressure vfurthermore being reduced by about one-third by withdraw-ing the oxygen from the vaporizer at 'a reduced pressure of about 0.6 atmosphere ab- 40 solute. The other half of the air to be resolved is blown, Without excess pressure, into an upper column, in which rectication takes place at approximately atmospheric pressure.

The compression necessary for the resolution of the air is therefore subdivided in such a manner that the compression is carried out to about one-half before the resolution andthereafter the other half takes place in that the oxygen which is removed from the vaporizer by suction at 0.6 atmosphere absolute is compressed to atmospheric pressure.

In this way a sumcient difference inv volume for the complete sublimation effect is obtained for one-half of the air to be resolved, is led at about 2 atmospheres absolute through one pair of l at 0.6 atmosphere absolute is alternately removed by suction.

According thereto a complete sublimation of the hoar frost which freezes out of the air led into the cold storage devices as -a result of the content of moisture and carbon dioxide, and which is temporarily deposited there, can be brought about without loss of energy.

II oxygen is to be recovered with an oxygen content of 42 per cent in the mixture produced, then the amounts compensate one another exactly, for one-half of the resolved air will come out of the apparatus as a mixture rich in oxygen, and the other half` as nitrogen, so that it is possible to introduce one-half ofthe air into each of the two pairs of cold storage devices. The one half is compressed and liquefied and `serves as wash liquid, the other halfr is blown in and the oxygen is washed out of it by the wash liquid.

When, however, a mixture richer in oxygen thanV a 42 per cent oxygen content is required, there is created a lack of agreement in the relative amounts o! blast air-oxygen mixture and compressed air-nitrogen, for the more oxygen the mixture is to contain the more nitrogen is separated out and the smaller is the amount of the mixture rich in oxygen.

II, for example, a mixture with a 47 per cent oxygen content is demanded, 0.55 cubic meter of nitrogen is separated per cubic meter of total air throughput, and 0.45 cubic meter of mixture with a 47 per cent oxygen content is recovered.

The enrichment of the wash liquid (which in this case consists of pure, liquid nitrogen) to 47 per cent omrgen requires 55 parts of blast air, while for the production of a per cent oxygen mixture only 45 parts of compressed air are required. Accordingly, parts of nitrogen must be led out through that pair of cold storage devices through which only 45 parts of compressed air can alternately be introduced and, on the other hand, 55 parts of blast air are alternately to be led counter-current through another pair of cold storage devices with respect to the 45 parts of oxygen mixture, which, of course, is not balanced with regard to the thermal equilibrium of the cold storage devices.

'Io equalize this lack of agreement more compressed air is led in through the one pair of cold storage devices than is actually needed for the formation of the necessary wash liquid, that is 55 parts instead of 45.

'Ihe ten parts of compressed air introduced in excess are again taken out of the resolution apparatus unliqueied at a pressure of 2 atmospheres absolute. They are iirst led through a counter-current cold exchanger, then through an air liqueer, and supplementarily are led through a counter-current cold exchanger, compressed further in a compressor to 10 to l5 atmospheres absolute, and again conducted through the cold exchanger in order to be forecooled in the latter to about 100 C. Subsequently they are detensioned to atmospheric pressure in an expansion engine, whereby they are cooled to 170 C. The exhaust is then after-cooled in the rst mentioned counter-current cold exchanger to about 190 C., and is blown in at the bottom of an upper rectification column.

As a result, the excess 10 parts or per cent of compressed air nally are utilized as blast air, thereby creating the quantitative equalimtion for the operation of the cold storage devices. In

-this manner, the amount of blast air lacking can be introduced through the nitrogen cold storage device, for which there would otherwise be an excess of nitrogen to be led out. Hence, only so much blast air need be led through the oxygen cold storage device as corresponds to the amount of oxygen which is led out.

This procedure differs fromv'that of my copending applicationin that the 4excess portion of air compressed to condensation pressure and which is removed-unliqueed from the low cooling zone of the apparatus in order to be detensioned in the expansion engine, is further compressed before it enters the expansion' engine, after being previously warmed to atmospheric temperature by cold exchange'with itself and is then again cooled to about 100 C.

The accompanying drawings illustrate an arrangement suitable for carrying out theV proee.

Referring to Fig. 1, fty-ve'per cent (in round numbers) of the amount of air to be resolved, ata pressure of about 2 atmospheres absolute, are led through lines I', I" and 2 alternately through cold storage devices A and A", and an equally large amount of separated nitrogen lis led 'out through line 3, 4' and 4" at atmospheric pressure.

The compressed air, to the extent of about 80 per cent, is resolved .in pressure column b into 43 per cent oxygen and almost purenitrogen, whereby there is produced from about one-half of the compressed air by liquefaction on the condenser side c of vaporizer c,|a liquid with an oxygen content of about 43 per cent, and as to the other half,

liquid nitrogen. 'Ihe 143 per cent oxygen liquid is now conveyed through line 5' into the lower quarter-of the upper rectification columnbwand the liquid nitrogen through line 6 to the uppermost tray of the same. On their way to the upper rectifier both liquids are led through the aftercoolers p (for the 43 per cent oxygen liquid) and r (for the liquid wash nitrogen), and are cooled by the gaseous nitrogen passing out of the upper column b through line 3.

About 45 per cent of the air to be resolved is led, at a pressure of about 0.1 atmosphere gauge by line 1', 1" and 8 alternately through cold storage devices B and B, and an equal amount of oxygen of an oxygen content of about 47 per cent is led out at a reduced pressure of 0.6 atmosphere absolute through line 9, i0' and I0". 'I'he blown-in air is introduced through line 8 into the bottom of the upper column, and ilowing up.

through the latter is led counter-current, iirst to the 43 per cent oxygen liquid and then to the liquid nitrogen, whereby the oxygen is washed out of the blown-in air and both liquids are enriched to an oxygen content of about 47 per cent.

-The portion of about 20 per cent of the compressed air which is not liquefied is led out through line I I, rst through a cold exchanger d, then through an air iiqueiier f, and finally through an additional cold exchanger g whereby this portion is heated to about atmospheric temperature. It is then compressed in compressor h to from 10 to 15 atmospheres absolute, led through line I2 again into cold exchanger g, Where it is forecooled to about 100 C.; conducted through line I3 into expansion engine Ic; detensioned in theolatter almost to atmospheric land linejl` as'exhaust into the upper column b". 'I hemitrogemseparated a gaseous state, is led a air to anexpansionengine and resolving the ex- Y l15 Sironi t 0.6g`, at ere.absolut e, valternately* through l `ivoili:iat atrriosplieric pressure from the top` of the 'uppercolumn' through line 3, passed through the 'after-coolers' rand pA and led` out alternately f through 1 cold'qstorage vdevices A' and A", while f. fthe .oxygenation anpxygen content of about 4 7 pen-Gentilisremovedy underv suction 'through line aporizer' `side c of `condenser c, at

cold` stora e devicesB' and B".

. nste' vt'conductinelthe excessfcompressed haust. in thefupper r.ectiier, this portion 'ofthe airfcan alsobe-rresolved in the'lower rectierat the'condensation pressure andunliqueiied nitro-` gen for theoperation 'of the expansion engine is taken out of the pressure column through line I I (Fig. 2).. which vnitrogenis vthen llikewise led through cold exchangerd,` liqueiierj and cold exchanger g'at about 2 atmospheresabsolutewhereby itis warmed to about atmospheric .temperature; compressedfurthr to 10 to 15 atmospheres absolute; led through line l2 into cold exchanger g where it is forecooled to about 100 C., and is then 'led through line I3 into expansion engine `K and `dete'nsioned `to atmospheric pressure in the latter. A fter further cooling-.to about 185 vC. in exchangerd, itis led through line'll (Fig. 2)

into cold "storage devices A and'A" and is led through. the latter out of apparatus.,y In this .way,'the necessaryamount of blast air-can likewise be brought into agreement with the amount of` oxygen led out because a llarger amount of oxygen is thereby produced in the pressure column, and less liquid wash nitrogen is poured in at the top of the upper column in an amount corresponding tothat of the nitrogen which is with-y drawn in a gaseous state from the pressure column forI-the operation of the expansion engine.

Therefore', the increased amount of oxygen producedin the pressure column without an increased amount of blast air, 'on the one hand,

produces a saving of lblast air and, on the other hand, the requirementv of blast. air is further diminished by the diminished-amount of liquid wash nitrogen which is poured in at the top of the upper column.

This mode of operation diers from the form in Fig. 1 only in that air from the bottom of the cold storage devices is not usedL for the operation of the expansion machine andl the exhaust subsequently resolved by blowing into the upper column, but that pressure nitrogen is taken from the pressure column in a gaseous state in order, after warming and greater compression with subsequent forecooling, to be detensloned in the ex pansion engine, and is then led out through the cold storage devices. after having previously been after-cooled by the pressure nitrogen to about 185 C.

According to this procedure the resolution of that portion which performs work in the expansion engine takes place before the detensioning and at an excess pressure, and nitrogen, instead of air, is led into the expansion engine.

A certain amount of highly compressed air is led into liquefier f at z, after having previously been forecooled to 45 C. in an ammonia refrigerating machine (not shown) and is liquefied by the portion of compressed air or nitrogen led out, in order to cover the unavoidable losses of cold.

The supplementary liquid is led through line I5 into pressure column b".

` 'The procedure of the present invention is characterized in that vinstead of the gas mixture being totally compressed, only about one-half is compressed, .whereas the other half is blown in. The compressed .portion is compressed to onlyabout one-half the extent required where a straight compression process is utilized. Further, the diflicultly boiling sepailated productV is removed Vunder reduced pressure from the evaporator side of the condenser and that portion of the gas mix'v ture which is simply blown in-uncompressed trav verses that pair of cold storagev devices or regenerators through which the diflicultly boiling separated-product is led out. This produces with respect to the amount of gas mixture which is blown in uncompressed,` the necessary difference in volume for a complete sublimation of deposited water and carbon dioxide. in the regenerators with-l out requiring the compression of a greater part ofthe gas mixture than is necessary to carry out the separation process. Also the recovery of oxygen with an oxygen content greater than 45 per cent Vis effected by compressing a portion of the gas mixture greater than that required for the formation of the wash liquid and conveying this added portion ofthe gas mixture to an expansion engine after it has been warmed, further compressed and cooled to about C. Furthermore, the'exhaust from the expansion engine is vcooled to a greater-extentby-cold Aexchange with the excess compressed vportion of the gas mixture or with themore easily boiling constituent thereoi' beforeit is conducted'through the regenerators lor led into the upper rectification column.

Since certain changes in carrying out the above process and in the constructions set forth, which embody the invention may be made without departing from its scope, it is intended that all mat- Havingdescribed my invention, what I claim V as new and desre to secure by Letters Patent is: 1'-v A process for the resolution of gas mixtures which comprises introducing a portion of a gas `mixture compressed 'to condenser pressure through a regenerator previously cooled by means of an easily boiling component of said mixture to a. recter, introducing another portion of said gas mixture uncompressed through a regenerator previously cooled by a diiiicultly boiling component into another rectifier, conducting liquidl formed in said first rectifier to said second rectiiler, conveying diiilcultly boiling component liquid from the second rectifier to the vaporizer side of a condenser and withdrawing separated dimcultly boiling component therefrom under reduced pressure, removing a portion of the compressed and cooled gas mixture, warming said removed portion by heat exchange with an added quantity of gas mixtureA which is introduced into said first rectifier, compressing, cooling, and detensioning to recover cold given up to the additional quantity of gas mixture, and reintroduclng into the process whereby cold and compression losses are reduced.

2. A process for the resolution of gas mixtures which comprises introducing aportion of a gas mixture compressed to a condenserv pressure through aregenerator previously, cooled by means of an easily boiling component of said mixture to a rectifier, introducing another portion of said c gas mixture uncompressed through a vregeneraby heat exchange with an additional quantity Vof A gas mixture which is then introduced into said first rectifier, compressing, cooling, and detensioning to recover cold given up to the additional quantity of gas mixture, and reintroducing into the process whereby cold and compression losses are reduced.

3. A process for the resolution of air into oxy-v gen and nitrogen which comprises compressing a portion of the air to condenser pressure, passing said compressed air through a regenerator which has previously been cooled by outgoing nitrogen, introducing the compressed and cooled air into a rectifier, passing another portion of air uncompressed through a regenerator which has previously been cooled by outgoing oxygen, introducing said cooled air into another rectier, conveying liquid from said first rectier to said second rectiiier, leading oxygen liquid from said second rectifier to the vaporizer side of a condenser in said first rectifier and removing oxygen therefrom under reduced pressure, removing a portion of the compressed and cooled air, warming said removed portion by heat exchange with an added quantity of air which is then introduced into said rst rectifier, compressing, cooling and detensioning to recover cold given up to the additional quantity of air, and reintroducing into the process whereby cold and compression losses are reduced.

4. A process for the resolution of air into oxygen and nitrogen which comprises compressing a portion of air to a pressure of about 2 atmospheres, passing said compressed air through a regenerator previously cooled with nitrogen and introducing said air into a rectifier; passing a portion of uncompressed air through regenerators previously cooled by outgoing oxygen and introducing said uncompressed air into another rectier; conducting liquid formed in the first rectier to the second rectifier, conveying oxygen liquid from the second rectifier to the vaporizer side of a condenser in the iirst rectier, removing oxygen therefrom under a reduced pressure of about 0.6 atmosphere absolute, removing about 10 per cent of the compressed air prior to rectification, passing said air through a plurality of heat exchangers whereby it is warmed including transfer of heat from an additional quantity of air thereto, thus liquefying the air, introducing the thus liqueed air into said first rectifier, compressing to from 10 to 15 atmospheres absolute, cooling to about C., detensioning in an expansion engine to about atmospheric pressure, whereby it is cooled to about C. to cover cold given up to the additional quantity of air, further cooling to about C. and introducing into said second rectifier whereby cold and compression losses are reduced.

5. A process for the resolution of gas mixtures into components, which comprises rectifying a .second rectiiier under substantially atmospheric pressure, withdrawing separated higher boiling component under a reduced pressure, removing a portion of the compressed gas mixture, warming said removed portion by heat exchange with an added quantity of gas mixture which is then introduced into said iirst rectier, compressing, cooling and detensioning to recover cold given up to the additional quantity of gas mixture, and reintroducing into the process whereby cold and compression losses are reduced.

6. In a process for the resolution of air into nitrogen and oxygen, the improvement which comprises compressingair to about 2 atmospheres, cooling in a regenerator, withdrawing a portion of the compressed and cooled air prior to resolution in a first rectiiier separating the remaining portion of the cooled air in said first rectiiier wherein liquid enriched in oxygen is obtained and subsequently resolved into nitrogen and oxygen in a second rectier, rewarming said portion by heat exchange with an additional quantity of air which is then introduced into said rst rectier, compressing, cooling and detensioning to about atmospheric pressure to recover cold given up to the additional quantity of air, further cooling, and then introducing into the second rectiiier whereby cold and compression losses are reduced.

7. In a process for the resolution of a gas mixture, the improvement which comprises compressing a gas mixture to condenser pressure, cooling in a regenerator, removing a portion of said compressed and cooled mixture, rewarming said portion by heat exchange with an additional quantity of gas .mixture which is subsequently subjected to resolution, compressing, cooling, then detensioningv to recover cold given up to the additional quantity of gas mixture whereby cold and compression losses are reduced, reintroducing into the process, and separating into components.

8. In a process for the resolution of air into nitrogen and oxygen, the improvement which comprises compressing air to about two atmospheres, cooling in a regenerator, withdrawing a portion of the compressed and cooled air prior to resolution in a rst rectifier separating the remaining portion of air in said rst rectier whereby a liquid enriched in oxygen is obtained and subsequently resolved into nitrogen and oxygen in a second rectifier, rewarming said portion by heat exchange with an additional quantity of air which is subsequently subjected to resolution, compressing to a pressure of about 10-15 atmospheres absolute, cooling to a temperature of about 100 C. and detensioning in an expansion engine to about atmospheric pressure to recover cold given up to the additional quantity oi' air: further cooling by countercurrentexchange with a portion of air immediately after it is withdrawn from the main body to a temperature of about 190 C.. and then introducing into a second rectifier whereby cold and compression losses are reduced.

9. In a process for the resolution of a gas mixture, the improvement which compises compressing a gas mixture to condensation pressure, cooling in a regenerator, removing a portion of said compressed and cooled mixture, rewarming said nortion including transfer of heat from an additional quantity of gas mixture thereto whereby the gas mixture is liquefied, introducing the thus liquefied gas mixture into the resolution process, compressing the removed and warmed portion, cooling, detensioning to recover cold given up to the additional quantity of gas mixture, and then cooling further, reintroducing inte the process, and separating into components.

10. In a process for the resolution of air into components, the .improvement which comprises compressing air to condensation pressure, cooling in a regenerator, removing a portion -of said compressed and cooled air, rewarming said portion including transfer of heat from an additional quantity of air thereto whereby the air is liquefied, introducing the thus liqueed air into the resolution process, compressing the removed and warmed portion, cooling, detensioning to recover cold given up to the additional quantity of air, and then cooling further to-a temperature of about -l90 C., reintroducing into the process and separating into components.

11. An apparatus for resolution of gas mixvtures comprising in combination a plurality of regenerators having regenerativepacking, means for eiiecting separation of the gas mixture into components, conduits for conducting the gas mixture from the regenerators to the separating means and from the separating means to the regenerator's, conduits for charging gas mixture to the regenerators and for discharging separated components therefrom, a conduit connected with said separating means for conveying a portion of the gas mixture to a series of heat interchangers, said conduit connecting with a coil in a rst exchanger, said coil connected with the outer space of a second exchanger` by means of a conduit, a conduit leading from the outer space of said second exchanger to the outer space of a third exchanger, a coil within said second exchanger through which an additional quantity of gas mixture may be conducted and cooled, a conduit for conducting said added gas mixture to the separatingmeans wherein it is subjected to resolution, a compressor in communication with the outer space of and with a coil in the third exchanger, a conduit leading from the coil in the third exchanger to an expansion engine, a conduit connecting said expansion engine with the outer space of said first exchanger, and a conduit from the outer space of the iirst exchanger leading to said separation means i'or reintroducing said portion into the system Whereby cold and compression losses are reduced.

12. In an apparatusv for the resolution o1' gas mixtures, a cooling and separating system in combination with a conduit for conveying a part of the gas mixture to a series of heat exchangers, said conduit connecting with a coil in a rst exchanger, said coil connected with the outer space of a second exchanger by means of a conduit, a conduit leading from the outer space of said second exchanger to the outer space of a third exchanger, la coil within said second exchanger through which an additional quantity of gas mixture may be conducted and cooled, a conduit for conducting said additional gas mixture to the separating means wherein it is subjected to resolution, a compressor in combination with the outer space of and with a coil in the third exchanger, a conduit leadingfrom the coil in the third exchanger to an expansion engine, a conduit connecting said expansion engine with the outer space of said first exchanger, and a conduit leading from the outerl space of said iirst exchanger for re-introducing said portion of gas into the system wherebyvcold and compression losses are reduced.

13. A process for the resolution of a gas mixture into components, which comprises rectifying a gas mixture compressed to condenser pressure and cooled, in a rst rectier, whereby lower boiling component in gaseous form and higher boiling component in liquid form are separated, rectifying the liquid so produced in a second rectier, withdrawing separated higher boiling component, removing a portion of compressed and cooled gas, warming said removed portion including heat exchange with an added quantity of gas mixture which is then introduced into said first rectifier, compressing, cooling and detensioning to recover cold given up to the additional quantity of gas mixture, and reintroducing into the process whereby cold and compression losses are reduced.

14. In a process for the resolution of a. gas mixture, the improvement which comprises compressing a gas mixture to condenser pressure, cooling by passing through a cold yielding zone, removing a portion of compressed and cooled gas, rewarming said portion including heat exchange with an additional quantity of gas mixture which is subsequently subjected to resolution, compressing, cooling, then detensioning to recover cold given up to the additional quantity of gas mixture, and reintroducing into the process whereby cold and compression losses are reduced.` 

